Wireless communication systems are widely deployed to provide, for example, a broad range of voice and data-related services. Typical wireless communication systems consist of multiple-access communication networks that allow users to share common network resources. Examples of these networks are time division multiple access (“TDMA”) systems, code division multiple access (“CDMA”) systems, single-carrier frequency division multiple access (“SC-FDMA”) systems, orthogonal frequency division multiple access (“OFDMA”) systems, or other like systems. An OFDMA system is adopted by various technology standards such as evolved universal terrestrial radio access (“E-UTRA”), Wi-Fi, worldwide interoperability for microwave access (“WiMAX”), ultra mobile broadband (“UMB”), and other similar systems. Further, the implementations of these systems are described by specifications developed by various standards bodies such as the third generation partnership project (“3GPP”) and 3GPP2.
As wireless communication systems evolve, more advanced network equipment is introduced that provide improved features, functionality, and performance. A representation of such advanced network equipment may also be referred to as long-term evolution (“LTE”) equipment or long-term evolution advanced (“LTE-A”) equipment. LTE is the next step in the evolution of high-speed packet access (“HSPA”) with higher average and peak data throughput rates, lower latency and a better user experience especially in high-demand urban areas. LTE accomplishes this higher performance with the use of broader spectrum bandwidth, OFDMA and SC-FDMA air interfaces, and advanced antenna methods. Uplink (“UL”) refers to communication from a wireless device to a node. Downlink (“DL”) refers to communication from a node to a wireless device.
For a wireless communication system using a relay node (“RN”), a wireless device may have difficulties selecting between a base station and the RN due to, for instance, UL and DL power imbalance. An RN such as an LTE Type-I RN can operate as a smaller base station. In an LTE system, a wireless device may choose a base station or RN based on the average DL signal strength, which may result in lower signal strength on the UL due to the UL/DL power imbalance. Alternatively, the wireless device may choose the base station or RN based on both DL and UL signal strengths.
As described in the LTE-A standard, a Type-I RN can have full radio resource control (“RRC”) functionality. Such RN can control its cell and can have its own physical cell identifier. Further, such RN can transmit its own synchronization channel and reference signal. Also, the wireless device can receive, for instance, scheduling information and hybrid automatic repeat request (“HARQ”) feedback from the RN and send control information such as a scheduling request (“SR”) signal, channel quality indicator (“CQI”) signal and HARQ feedback signal to the RN.
In a heterogeneous LTE-A network using a plurality of base stations and Type-I RNs, such network may have a significant difference between base station transmission power and RN transmission power. A wireless device may provide a UL transmission that is received by a base station and a RN. The received power from such transmission may be substantially dependent on the propagation path between the wireless device and the base station, RN or both. In some circumstances, the wireless device may receive a stronger DL transmission from the base station, while the RN receives a stronger UL transmission from the wireless device, leading to a UL and DL power imbalance. This disclosure describes various embodiments including for resolving such power imbalance in a multiple-serving node wireless communication system.
Skilled artisans will appreciate that elements in the accompanying figures are illustrated for clarity, simplicity and to further help improve understanding of the embodiments, and have not necessarily been drawn to scale.